USGS Washington Water Science Center
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WA214 - Status of the Saltwater Intrusion Of Coastal Areas in Washington - Completed FY1982
Problem - Washington State has many miles of coastline on the Pacific Ocean. Ground water is the chief source of fresh water in these areas. Heavy demands are being placed on coastal aquifers known to be hydraulically connected to saltwater bodies. A reconnaissance of saltwater intrusion was conducted in 1966-68 and indicated that demands on the ground water had led to moderate intrusion in several areas and that intrusion was incipient in others. Development has continued since the 1966-68 study and thus there is a likelihood that saltwater intrusion has also increased. The questions posed in this study are: (1) Has saltwater intrusion in Washington increased or decreased since the 1966-68 study? (2) Has intrusion occurred in any of the areas developed since 1966-68? (3) What is the extent and degree of intrusion, if any, in those areas previously described as having incipient intrusion problems?
Objectives -The objectives of this study are to (1) determine the present location, extent, and degree of saltwater intrusion in coastal Washington; (2) designate those areas where future intrusion might occur; and (3) determine if the extent or degree of intrusion, as described by Walters (1971), has substantially changed.
Approach - The criterion used to determine the presence of saltwater intrusion will be the chloride content of ground water from wells located within 1 mile of the coast. The wells will be sampled once only, during late spring or summer, and emphasis will be placed on sampling those wells whose producing zones are below sea level. The data collected will be compared to those collected in the 1966-68 study. This is a qualitative investigation; no attempt will be made to determine the quantity of saline water involved, nor of the position of the freshwater/saline-water interface. Ground-water levels will be measured in the wells prior to sampling whenever possible, but no attempt will be made to relate chloride content to pumpage, tidal fluctuation, or changes in ground-water level.